maybe others can chime in on this, but I would think you might run into trouble with acidosis... feeding highly fermented feeds and spring pastures that are very high in digestible energy.
Im not an expert, just something to think about. I am trying to get my hands on a pH meter to check the manure of my cows right now. they are still pretty runny after several weeks on grass, and seem to be overheating easily right now... have a hunch something isnt right. pasture is pretty hot, lot of white clover, birdsfoot trefoil and p. ryegrass